To build the campfire, you will need to expend the following Resources:

As Vale:

4 Wood

2 Tinder

As Eva:

1 Dry Wood

For more information on gathering or crafting each Resource, click on the above links.

Once you have the required Resources in your Inventory, Use the campfire. This will bring up a window in your HUD. If you have the required Resources in your Inventory, you can click on the green button to build the campfire. After you click on the green button, a countdown timer will appear on screen, during which time your character will perform an animation. Once the campfire is built, an animated image of a fire will appear on-screen at the campfire location, and, if it is nighttime in-game, a nimbus of light will surround the location. You will also gain some Experience Points.

The campfire will last for two in-game days before it has to be built again.

The campfire serves two main purposes: repelling mosquitoes and cooking fish.

Once built, the fire will automatically repel mosquitoes, preventing the pests causing your character to prematurely awaken from sleep.

An active fire can also be used to cook fish. To cook fish, have raw fish in your inventory, as well as a free inventory slot or a slot containing a stack of fewer than 10 cooked fish, and approach the campfire. Once the object interaction menu for the campfire appears, click on the Cook Fish button, or press the corresponding hotkey. This will remove one raw fish from your inventory and replace it with one cooked fish. Repeat until you have as many cooked fish as you desire.

The campfire also acts as a source of light, making the area immediately around the campfire significantly brighter during the night. In-game dialogue, spoken by your character when you click the button for Info about the campfire, implies that the campfire improves your campsite's security.